Digging in my yard... what is it?

[FinelineGraffix]

found some intresting things in my yard... 

ive found a few pieces like this 

[FinelineGraffix]

[Kane]

It looks sedimentary to me, but the whole piece is not - from what I can gather - a fossil. There appears to be a few small flecks in the cross-section picture that might suggest some tiny marine fossils like brachiopods. The patterning on the outside may likely be the result of geologic processes. Keep digging!

[FinelineGraffix]

 

[FinelineGraffix]

 

[FinelineGraffix]

a few more

[ynot]

They look like geologics to Me also. Some of the pieces look like they could be an internal cast of a shell, but I am uncertain of that.

The last 3 are definitely geologic and not fossil.

 

Regards,

Tony

[FinelineGraffix]

thanks for the info that does help!

 

-nick

[ynot]

Last one looks like a fractured rock with remnants of mineral veins on parts of it.

[BobWill]

The first one looks a bit like the internal mold of a clam as Tony said. If so, they don't give us enough information for identification since the external ornamentation would not show up inside. Concretions can form around creatures that have fossilized so it can't hurt to bust the spherical ones open to see. If you have naturally occurring sedimentary rock in the area there can certainly be fossils to look for. Find a geological map for Minnesota to see what you might expect to find or contact the closest rock club for suggestions about where to look if this sparks an interest for you.

[GeschWhat]

Welcome to the forum!

 

The first one looks like a cast of something to me as well, but I'm not aware of any bivalves in the areas around here that I'm familiar with. Where in MN was this found? Perhaps @Bev can help.

[Bev]

Congratulations! GREAT FIND! 

 

Definitely an internal mold of something. Yes, we do have bivalves around here. You are seeing brachiopods and bryozoans that infilled with the sediment or were trapped as they were scavenging the innards of the creature. If you are in southeastern MN from the Twin Cities on down you are in the Ordovician, so this fossil mold would be roughly from 425 to 480 years old - older than the dinosaurs.  :-D

 

Great conversation piece for your mantel. 

 

I have a great ID sheet on my fossil adventure blog that you can print off for FREE that will help you to identify other fossils you may find in your yard or elsewhere. Lots of info on the site and the blog.

[Bev]

Here is the Ordovician ID Sheet

 

Here are two internal molds of gastropods I collected today in Fillmore County, MN - SE MN. On the left is a Fusispera sp. gastropod and on the right is a Maclurites sp. gastrpod - the Maclurites are an index fossil of the Ordovician which means that they only lived in that time. Take a close look at the Maclurites, although an internal cast it still has a bit of the shell, I believe, right at the eye. That shell fragment is a true fossil from 450 mya.

 

[Wrangellian]

Could it be (the internal mould of) a spiral nautiloid? It's so hard to tell because whatever it might be is missing so much.

[FossilDAWG]

I wish the new format allowed posts, and ideally images, to be numbered so we could be clear what image is being discussed.

 

That being said, the second photo in your second series of images is clearly a piece of a nautiloid cephalopod.  You can see the surface of one chamber (called a camera) is intact, there is a second one broken through by your thumb, and a piece of the outer shell showing some sutures is present as well.  This seems to be the same specimen as the one you show in your first series of photos?  The "squiggly lines" are infills of a kind of burrow trace fossil called Thalassinoides.  These were made by "worms" (a catch-all term for "unknown soft-bodied burrowers") burrowing through the sediment that filled the nautilod shell after the nautiloid died and was buried in the sea-floor sediment.

 

Large cephalopods, and Thalassinoides burrows, are characteristic of the Ordovician Galena Group which is widely exposed in Minnesota.  Most of your other specimens do not seem to be fossils.

 

Don

[Harry Pristis]

19 hours ago, Bev said:

[snip]

Definitely an internal mold of something. Yes, we do have bivalves around here. You are seeing brachiopods and bryozoans that infilled with the sediment or were trapped as they were scavenging the innards of the creature. If you are in southeastern MN from the Twin Cities on down you are in the Ordovician, so this fossil mold would be roughly from 425 to 480 years old - older than the dinosaurs.  :-

[snip]

 

It's not a mold, Bev, and certainly not an "internal mold" which is a nonsensical term.  It's a cast.  Are you suggesting that brachiopods and bryozoans are scavengers??  As far as I know, they are filter feeders.  Can you explain?

[Bev]

On 2/20/2017 at 11:31 AM, Harry Pristis said:

 

It's not a mold, Bev, and certainly not an "internal mold" which is a nonsensical term.  It's a cast.  Are you suggesting that brachiopods and bryozoans are scavengers??  As far as I know, they are filter feeders.  Can you explain?

Hi, Sorry I've been absent, but very sick...

 

Okay, Remember Caleb? He was the foremost expert on fossils in this area, especially trilobites. Caleb told me that these were internal molds of whatever. Cast may be a more appropriate term, I don't know. I'm just using the term I was exposed too. I don't know enough to suggest anything on brachs and bryos - yes they are filter feeders but they also end up in most of our "internal molds" which strikes me as scavenger behavior or they just set up shop inside the decomposing critter (also not a technical term)  to filter feed because...??? OR were swept in by currents. I don't know. I'm an old woman, an amateur, and just love fossil hunting and learning about this stuff. I will NEVER have your level of knowledge - and so many others here - but I love to fossil hunt and share the experience and fun. Bev  :-)

 

[Harry Pristis]

You are a teacher, Bev, and as such, much is expected of you.  Sorry you've been ill . . . get well soon!

[GeschWhat]

1 hour ago, Bev said:

Hi, Sorry I've been absent, but very sick...

 

Okay, Remember Caleb? He was the foremost expert on fossils in this area, especially trilobites. Caleb told me that these were internal molds of whatever. Cast may be a more appropriate term, I don't know. I'm just using the term I was exposed too. I don't know enough to suggest anything on brachs and bryos - yes they are filter feeders but they also end up in most of our "internal molds" which strikes me as scavenger behavior or they just set up shop inside the decomposing critter (also not a technical term)  to filter feed because...??? OR were swept in by currents. I don't know. I'm an old woman, an amateur, and just love fossil hunting and learning about this stuff. I will NEVER have your level of knowledge - and so many others here - but I love to fossil hunt and share the experience and fun. Bev  :-)

 

I hear "internal mold" all the time, too. But, like you I am an amateur. Feel better! 

[ynot]

1 hour ago, Bev said:

- yes they are filter feeders but they also end up in most of our "internal molds" which strikes me as scavenger behavior or they just set up shop inside the decomposing critter (also not a technical term)  to filter feed because...??? OR were swept in by currents. I don't know.

Except for the "scavenger" and the "I don't know" parts this all sounds good to Me

In addition many of the stationary animals of a reef start thier life as plankton. As such they grow wherever they land, any suitable surface (like the inside of an empty shell) will do. Not scavenging just colonizing.

 

I have to agree about the "internal mold" . It is a cast or a steinkern.

 

Tony

[GeschWhat]

Please forgive me if I come off as argumentative, that is never my intent. I think perhaps we sometimes misuse the term "internal mold," but it is a legitimate term. I found this which seems to explain it pretty well (and I learned something). 

[Harry Pristis]

I see how you could be mis-led by this web-page description of "internal mold."

 

Let's take a clam as an example.  A clam dies, is buried in sediments, and the soft-parts quickly decompose.  The valves remain sealed.  With enough time, the surrounding sediments may form an external mold of the valves.

 

Or, the buried clam valves may open, allowing infiltration by fine sediment.  With enough time, the surrounding sediments may form an external mold of the valves AND an internal cast of the interior of the clam. 

 

This internal cast is formed within a mold (the clam valves).  The actual  clam valves are the closest we come to an true internal mold.  However, what we typically see are internal casts after the clam valves have long-ago dissolved away.  If the clam valves are intact, their potential to be an internal mold is irrelevant.

[abyssunder]

I think, Thalassinoides are generally a little more larger than the traces in question and their abundance is considered to be dated to the Mesozoic (200 MY after) , but I think, that's could be clear that the traces in question are made by worms, not crustaceans.
Btw, what is the scale for the SQ, the hand? If that, the diameter of the supposed cephalopod could be around 12-14 cm?

[Bev]

Harry: "This internal cast is formed within a mold (the clam valves).  The actual  clam valves are the closest we come to an true internal mold.  However, what we typically see are internal casts after the clam valves have long-ago dissolved away.  If the clam valves are intact, their potential to be an internal mold is irrelevant."

 

Clear as mud to me... I have seen external molds of gastropods and have a fair number of them. Nearly all of our Maclurites are internal molds. I make casts using internal and external molds make of plastic from my fossils by filling them with plaster of Paris - that is a cast to me and what the article/link seemed to say also.

 

So, are you saying that the truly scientific correct term for external and internal molds is "external and internal casts"??? Don't use the word mold, substitute it with the word cast and I'll be safe???  This is a lot to wrap my little pea brain around...

[EMP]

Cephalopod seems interesting. My first guess was an Isotelus chunk but I'm way out of my comfort zone.